Free piston engine system



Jan. 28, 1964 H. KosoFF 3,119,230

FREE PISTON ENGINE SYSTEM Filed May 10, 1961 INVENTOR. HAROLD KOSOF F YEQMWEKWMEM ATTORNEY United States Patent Ofifice 3,119,236 Patented Jan. 28, 1964 3,119,230 FREE PISTDN ENGINE SYSTEM Hamid Kosoti, 1203 Hale St, Philadelphia 11, Pa. Filed May 10, 1961, Ser. No. 199,039 13 Gaines. (Cl. 619) This invention relates to energy conversion apparatus and in particular to apparatus for converting the out put energy of a free piston engine to hydraulic pressure for operating a hydraulic-pressure-driven apparatus.

Hitherto, gas operated turbines have been the means for converting the output from a free piston engine to shaft rotation. Turbines are costly, unresponsive to rapid changes in operating conditions, heavy, and bulky. Since turbines are powered by relatively low pressure gas, they require large manifold systems to create the total power necessary. In addition, when coupled to free PlS- ton engines, turbines require conventional power regulating means such as mechanical throttle devices which introduce power losses and often require costly and compleX servo-mechanical components.

It is therefore a general object of this invention to provide novel means for converting the output of a free piston engine into work such as shaft rotation in a manner which is efficient, hig hly responsive, and which requires relatively inexpensive, light, and compact devices.

A primary object or" this invention is to provide a novel power source characterized by compactness and a high power output-to-weight ratio.

Another object of this invention is to provide, in a novel system for converting the output of a free piston engine to drive a fiuid motor, means for regulating the rotational energy produced without using known wasteful throttling devices.

Still another object of this invention is to provide means using few elements for regulating the output of a tree piston engine coupled to a fluid motor efficiently, responsively, and reliably.

Other objects of this invention will be apparent to those skilled in the art upon perusal of the drawing, specification, and claims herein.

In accordance with my invention I provide a system in which the output of a free piston engine is used to drive a fluid motor. I provide a hydraulic coupling system between the engine and the motor in which a (hydraulic medium is used for transmitting energy from the free piston engine to the fluid motor. An important feature of my invention is the provision of an efficient and simple pressure-regulating device acting upon the liquid medium for regulating the output of the fluid motor.

The sole figure depicts schematically and partially in section a free piston engine and fluid motor constructed according to one form of my invention.

A free piston engine 1 is provided which has pump chambers 24 that have been adapted for pumping liquid rather than gases. The engine consists of a combustion chamber 11, two opposed pistons 40, and two rebounce chambers 5i? and two auxiliary chamber 28. in a conventional free piston engine the air compressed by the action of the pistons is used to charge and scavenge the combustion chamber of the gaseous products of combustion. Since the medium compressed by the engine in my system is hydraulic, other means for providing compressed air for accomplishing the charging and scavenging function are provided. As shown, a turbosuperoharger fail is the source of the compressed air. The turbosupercharger consists of a turbine 31 and a compressor 32 attached to a common shaft 33 which passes through a dividing wall 35 within a housing 39 and is journalled in the walls of the housing. The wall 35 is constructed to keep the exhaust gases in the turbine section of the turbosupercharger 30 out of the compressor section and vice versa. Upon exposure of the combustion chambers exhaust ports 7% and intake port 7-1 to the combustion chamber on the outstroke of pistons it the exhaust products from the combustion chamber 11 pass through conduit 34 to drive turbine 31 which, in turn, drives the compressor 32. Compressed air is thereby conducted to the engine cornb-ustion chamber 11 via conduit 36. Conduits 37 and 38 are the intake and exhaust lines respectively. Starting the engine may be accomplished by setting off an explosive material such as gunpowder placed in a cylindrical receptacle 73 which opens, through an aperture 74, into the combustion chamber 11. The explosive may be set off by percussion means (not shown) for example. Of course, other means of starting the engine may be employed if desired.

Since the engine 1 should pump liquid at a high pressur (1,000 p.s.i. and higher, for example), each pump chamber 24 is smaller than the pump chamber of a conventional free piston engine of equal power output. Each pump chamber is arranged with respect to the other parts of the engine 1 in a way which is superior to conventional free piston en ine configurations since only one seal is required for the pump chamber. Furthermore, the smaller pump chamber diameter permits the walls 42 of the cylinder to be thinner. In addition, the contents of the pump chambers less likely to be contaminated by the combustion products from the combustion chamber, and the combustion within the chamber 11 coincides with the discharge st okes of the engine, hence less energy need be stored by the irebounce chamber than is the case in many conventional free-piston engines.

Fluid intake ports 7 of the pump chamber portion 24 of the engine 1 connect with a conduit 3 which leads to the output port 5 of a fluid motor 2. Toward the end of the compression (i.e., inward) stroke of the pistons 40 the port 7 is uncovered by the movement of the piston. To keep the liquid during the compression stroke of the pistons from entering the pump chamber 24, via conduit 1d, there are provided pump output valves 25 comprising flexible metal strips pinned to the inner projections 41 of the wall 42, the strips 25 covering apertures 27. Output ports 6 are coupled to conduits .113 which also lead to the fluid motor 2.

A fluid motor 2 is shown which may be, for example, a conventional rotory-type fluid motor having a cylindrioail housing 2% containing a rotor 21 fixedly mounted on a shaft 3 which is eccentric with respect to the housing 20 and which has radially siiding vanes 22 mounted in radial channels 23 therein. The liquid medium 13 is applied to the motor 2 under pressure at its intake port 4 from the conduit 14 which connects to the output port 6 of the engine 1. The hydraulic pressure causes the vanes 22 to move the rotor 21 in a rotary direction. As the shaft 3 rotates, those of the vanes that approach the upper or narrower part of the housing 269 will be urged inward in their respective channels toward the shaft until, as the shaft rotates further, they are ur ed outwardly by appropriate bias (such as by the springs shown) applied to them in the channels 23. The motor output shaft 3 may be used to impart motion, for exampie, to a propeller, a set of wheels, or similar conventional driving means.

Conected to the intake and output ports 7 and 6 are in conduits 8 and it? which respective-1y carry the low pressure and high pressure liquid 13 to the corresponding motor ports 5 and 4 Chambers 9 and 12 communicate with conduits 8 and 11 for the purposes to be explained in some detail below. The pressure at the port 4 for driving the motor 2 is generated within the conduit 19 by the output of the pump chamber portions 24 of the 3 engine 1 which generates nydraulic pressure transmitted by the medium 13.

For satisfactory operation of the free piston engine, the stroke of the pistons must be maintained as constant as possible, that is to say, the most inward position and the most outward position of the pistons should be almost invariant. As the pressure at port 6 and the quantity of liquid displaced per stroke is changed in response to the work performed by the motor 2, the stroke of the piston will be affected. If the most inward position of the pistons deviates from normal, the pressure in rebounce chambers Si will adjust because of the action of vents 51 and orifices 52a and 52]), the latter communieating with one another and with a source '75 of pressure by means of conduit 53. A by-product of this action is synchronization of pistons 44). A more detailed description of this structure and its operation can be found in my copending application Serial No. 76,933, filed Dec. 19, 1960. Conversely, if the most outward position of the pistons changes, the pressure in the bellows type of servomotor 56 and in the aperture 53 changes correspondingly. The bellows 555 communicates with the chamber 11 by means of a conduit 57 which passes through an aperture 64 in a mounting structure 63 and is connected to an aperture 72 in the wall The interior of the bellows also is coupled to the atmosphere by means of the aperture 62 in the member 63. The bellows is mechanically connected by a link 59 to a fuel meterinjector 50. Movement of the bellows to the left increases the fuel (i.e., volume per unit time); movement of the bellows toward the right decreases the fuel rate. The operation of the movement of the bellows 56 and link 59 as a function of the outstroke of the piston is described in more detail in my copending application, Serial No. 93,094, filed March 3, 1961.

Connected to the injector es is a conduit 43 which communicates with a fuel source 65. Conduit 44 couples the injector 69 to an injector nozzle 65 which injects the fuel into the combustion chamber 11. The injector 69 is described in more detail in US. Patent 2,425,850, issued on August 19, 1947, to R. 1. Welsh.

In order to understand more readily how the system pictured in the sole figure works, I have set forth below some underlying principles of operation of a free piston engine and a fluid motor. The power outputs of the free piston engine 1 and of the fluid motor 2 are equal to the respective products of (1) the pressure difference existing between their intake and output ports and (2) the volume of liquid displaced by each per unit time. Thus the output power of the engine 1 is equal to the difference in the pressure of the liquid at the engine pump ports 6 and 7 multiplied by the volume of liquid displaced by the engine per unit time. The output power of the fluid motor is equal to the product of the difference in pressure existing at the intake port 4 and the outlet port 5 multiplied by the volume of liquid displaced by the motor per unit time.

The output from the motor 2 may be controlled by varying either the difference in the pressure between its ports 4 and 5 or by varying the amount of liquid it displaces. One way to change the amount of liquid displaced per unit time would be to change the speed of the motor shaft 3. While the shaft speed could be varied by mechanical devices coupled to it or to other driven elements of the driven device, this is highly undesirable as it would require complex and expensive gearing or braking components which would also be relatively bulky. It is much more preferable and practical to change the motor output by varying the torque. Since its torque is proportional to the difference in pressure at ports 4 and 5, and since this pressure is related to the pressure at engine ports 6 and 7 its torque can be controlled by acting on the hydraulic coupling between the engine and the motor.

In accordance with an important feature of my invention I provide means for maintaining a constant low pres sure in conduit 8 (and at ports 5 and 7) and for controlling the pressure in the high pressure conduit 10 (and at ports 4 and 6) thereby controlling the power output from the motor and the engine. For the purpose of the invention as shown, the engine, at speeds of the motor shaft 3 below its maximum, will displace a greater volume per unit time than the motor, and the pressure in the low pressure conduit 8 will remain near zero. To demonstrate that the pressure in the conduit 8 is near zero, it should be appreciated that under normal operating conditions the actual liquid displaced by the engine is less than the are-determined displacement of the engine. The difference will exist as a near vacuum in the pump chamber 24 of the engine, i.e., the pump chamber will only be t. ally filled with liquid at the start of the pumps output stroke. To assist in maintaining the pressure in the low pressure conduit 8 near zero, an accumulator 9 is coupled thereto. This accumulator accepts the fluid 13 from the motor output port 5 during the outstroke of the pistons 4%. In so doing this accumulator 9 smooths out the pressure pulses in the low pressure conduit caused by having a continuous liquid output from the motor and a discontinuous liquid intake by the engine. The accumulator 9 also prevents stalling of the motor by preventing pressure build-up in the low pressure conduit 8.

As stated above, I provide pressure-regulating means operative on the high pressure conduit 10 which regulates the output torque of the shaft 3 of the motor. To control the pressure in the high pressure conduit 15 a pressure regulator comprising a chamber or liquid store 12 is provided which communicates with the conduit 19 by means of conduit 26. I also provide a source 15 of gas under pressure as the means which varies the pressure in chamber 12. Source 15 communicates with chamber 12 via pipe 14, there being a valve 16 located in the pipe 14. Branching oil from pipe 14 is a pipe 18 in which a valve 19 is inserted. The end of pipe 18 has an opening 17 which communicates with the ambient atmosphere. It the valve 19 is closed, opening the valve 16 will permit the desired amount of gas from source 15 to enter the chamber 12 and increase the pressure acting on the liquid stored therein. If it is desired to lower the pressure in chamber 12, the valve 16 is closed and the valve 19 is opened to the desired extent. In practical usage the valves 16 and 19 may be mechanically coupled to provide simultaneous complementary action. By the described means the pressure in line 10 may be varied be tween that of source 15 and that of the atmosphere. Alternatively, either one of the valves 16 or 19 may be replaced by a small orifice.

In addition to assisting in regulating the pressure in the high pressure conduit 10, the chamber 12 also serves as an accumulator for smoothing out the pressure pulses between the discontinuous liquid output of the engine and the continuous liquid intake of the motor. Also, the chamber 12 serves as a liquid store for providing liquid as needed to the chamber 24'; and to the accumulator 9. As motor 2 tends to slow down, the liquid in pump chamber 24 and in accumulator 9 tends to empty with a corresponding increase in the liquid in accumulator 12. As motor 2 tends to speed up the converse is true. At zero speed of the motor shaft 3, the accumulator 9 and the pump chamber 24 would be empty. At maximum speed of the motor shaft, both the accumulator 9 and the pump chamber will be full of liquid. For intermediate speeds there corresponds an intermediate amount of liquid in the accumulator and pump chamber. Thus, as the motor shaft speed increases, fluid leaves the liquid store 12 and enters the accumulator 9 and pump chambers 24. Conversely, on decreased motor shaft speed, fluid leaves the accumulator and pump chambers and enters the liquid store 12. It may be desirable to connect a duct (as shown) between the pump chambers 24 to maintain equal fluid pressure therein at all times.

Thus, my invention provides means for varying the pressure in the high pressure line while keeping the pressure in conduit 8 substantially uniform, i.e., near zero. Since the pressure at the ports of the engine and the motor are thereby varied, the torque of the motor will vary and the speed of shaft 3 can be controlled.

The described engine system is particularly adaptable for use in aircraft. By eliminating structures such as the crankshaft, connecting rods, and their supporting members which are found in conventional internal combustion engines and also by operating as a two-cycle engine with one combustion chamber, the power generated by this engine is much greater than that of a conventional engine of equal weight. Since the engine is dynamically balanced, it is free from vibration which in turn allows smaller and lighter support members.

The few moving parts of the engine, the elimination of all conventional throttling devices, and employment of the diesel principle with optimum scavenging of the combustion chamber enable the efficiency of this engine to be much higher than that of a conventional engine. Consequently, lesser amounts of fuel need be carried and the useful payload of an aircraft may be increased. Also, the fewer parts of this engine make it more reliable. Since the few parts that do move do so under no force at right angles to their direction of motion, there will be little or no wear.

Since the normal speed of the fluid motor is near that of an aircraft propellor, reduction gears are not necessary. The high efficiency of the engine will allow the use of a lighter and smaller cooling system. The smaller size of the engine and cooling system permits reductions in the frontal cross-section of the aircraft thereby also increasing its operating range or payload.

Many of the advantages cited above also apply to the use of this system in automobiles and other surface vehicles. Elimination of vibration will enhance the riding qualities of the vehicle. By coupling the fluid motor directly to the wheels of the vehicle, the transmission, clutch, driveshaft, and differential may be eliminated. Gear changes can be eliminated with a consequent improvement in riding qualities. Reversal of direction of motor rotation may be effected by providing for cross couplings of the fluid connections at the motor ports 4 and 5. With minor changes from the system as shown, braking can be effected by reversing the action of the fluid motor to that of a fluid pump. In this manner the energy stored in stopping the vehicle can be applied to the wheels upon starting and this will further improve fuel utilization.

Since my novel engine has a very high efficiency, it is possible to make a cooling system much smaller and using the air cooled type. Thus, radiators, water pumps, cooling fluid, and other parts found in automobile cooling systems may be eliminated. Because of the simplicity of this engine usual maintenance required by conventional automobile type engines will be greatly reduced.

I claim:

1. In combination: a free piston engine which includes means for developing pressure in a liquid and also includes a number of rebounce chambers corresponding to the number of pistons therein, a fluid motor, means including hydraulic means for coupling said pressure-developing means to the input of said motor said rebounce chambers being constructed to be free from any liquid and to supply the predominant restorative rebounce force for the pistons of said engine, whereupon said fluid motor is driven in response to the operation of said engine, and means connected to said coupling means for regulating the pressure within said hydraulic means and thereby controlling the output speed of said fluid motor.

2. In combination: a free piston engine which includes means for developing pressure in a liquid and also includes a number of rebounce chambers corresponding to the number of pistons therein, a fluid motor, and a hydraulic system coupled between said engine and said motor, said hydraulic system including a first means for conveying a hydraulic medium, said first means being connected between said pressure-developing means of said engine and the input to said motor, said rebounce chambers being constructed to be free from any liquid and to supply the predominant restorative rebounce force for said pistons, said first means having coupled thereto means for modifying in a continuously variable manner the pressure of said medium therein, and a second bydraulic conveying means coupled between said engine and the output of said motor.

3. The combination according to claim 2 wherein said means for modifying the pressure in said first means includes a source of a gas under pressure.

4-. In combination: a free piston engine having a cylinder with two opposed pistons disposed for travel therein and two pump chambers in which said respective pistons also travel, said engine also having two rebounce chambers, a fluid motor having intake and outlet ports, first hydraulic means coupled to said pump chambers and to said intake port, said first means being constructed to contain a hydraulic medium whose pressure is increased by the action of said pistons in said pump chambers, second hydraulic means coupled to said pump chambers and to said outlet port, said second means containing said medium under pressure considerably lower than the medium in said first conveying means, said rebounce chambers being constructed to be free from any of said hydraulic medium and to supply the predominant restorative rebounce force for said pistons and means operative upon said first hydraulic means for adjusting the pressure of said hydraulic medium therein over a predetermined range thereby to control the speed of said fluid motor.

5. The combination according to claim 4 wherein said pressure-adjusting means includes a source of a gas under pressure.

6. The combination according to claim 5 wherein said cylinder and the opposed faces of said pistons bound a combustion chamber and wherein means communicating with said combustion chamber are provided for scaveng ing and charging the latter.

7. In combination: a free piston engine having a cylindrical housing with two pistons therein, each of said pistons having shaft and head portions, two pump chambers in which said shafts travel, a combustion chamber bounded by said housing and opposing faces of the head portions of said pistons, two rebounce chambers between said pump chambers and said combustion chamber; a fluid motor having intake and outlet ports; a first hydraulic system coupled to said pump chambers and to said outlet port, said first hydraulic system including a hydraulic medium a relatively low pressure; a second hydraulic system coupled to said pump chambers and to the intake port of said fluid motor, said second hydraulic system including said hydraulic medium at a pressure which is considerably higher than the pressure in said first hydraulic system, said pressure in the hydraulic medium in said second system being built up by the action of said pistons on their outstrokes; means coupled to said combustion chamber between the opposing faces of said pistons for scavenging and charging said combustion chamber, means including gas pressure means coupled to said second hydraulic system for adjusting the presure of the medium therein thereby controlling the torque produced by said motor; means including a source of gas under pressure interconnecting the rebounce chambers of said engine; said rebounce chambers being isolated from said hydraulic means and being free from said hydraulic medium, said rebounce chambers supplying the predominant restorative rebounce force for said pistons, a plurality of vents communicating with said rebounce chambers which cooperate with said last-named interconnecting means for synchronizing said pistons, and means coupled to said combustion chamber and to a fuel 7 injection system therefor for controlling the rate at which fuel is injected by said injection system into said combustion chamber.

8. The combination according to claim 7 wherein said scavenging and charging means comprises a turbosupercharger, wherein said first hydraulic system includes an accumulator, wherein said means for adjusting the pressure of said medium includes another source of a gas under pressure and a hydraulic medium storage chamber coupled to said other source of gas and to said second hydraulic system, and wherein valve means are provided for regulating the flow of gas from said other source to said storage chamber.

9. The combination according to claim 7 wherein said means for controlling said fuel rate includes conduit means adapted to be connected to said combustion chamber on the outstroke of said pistons, a bellows having one end thereof held in a fixed position and connected thereat to said conduit means and also to the ambient atmosphere and means at the other end of said bellows adapted for coupling movement of the free end of said bellows to said fuel injection system.

10. An internal combustion engine-fluid motor system comprising: a free piston engine having a pair of pistons having respective opposed heads and shafts connected thereto and being arranged for axial movement within a cylinder, said pistons being constructed and arranged to be repelled from one another in response to the explosion of a gas ignited in a combustion chamber between the heads of said pistons, said engine also including two rebounce chambers behind the heads of said pistons, said rebounce chambers being free from any hydraulic medium and constructed to supply the predominant restorative rebounce force for said pistons, and two pump chambers in which the shafts of said pistons move, means coupled to said combustion chamber for scavenging said chamber and supplying compressed air thereto, means coupled to said combustion chamber and to said rebounce chambers for maintaining the stroke displacement of said pistons relatively constant and synchronizing the movement of said pistons, a fluid motor, a first conduit network coupled between said pump chamber and the input to said fluid motor, said first network containing a hydraulic medium under high pressure which drives said fluid motor in response to the operation of said engine, means including a source of a gas under pressure coupled to said first network for controlling the torque produced by said fluid motor by varying the pressure of the medium in said first conduit network, a second conduit network in which said medium is contained under relatively low pressure coupled between said engine and the output of said fluid motor, said second network including an accumulator for smoothing out hydraulic pulses present in said second network, said first and second networks being completely separated from said rebounce chambers.

11. The system according to claim 10 wherein said first conduit network includes two auxiliary chambers adjacent said respective pump chambers and wherein valve means are provided between said auxiliary chamnetwork.

13. The system according to claim 11 wherein said auxiliary chambers and said pump chambers communicate by apertures in their common wall and wherein said valve means comprises two strips of flexible material having first ends fixedly mounted to said common wall, said strips covering said apertures on the compression strokes of said pistons.

References Cited in the file of this patent UNITED STATES PATENTS 2,230,760 Pateras Pescara Feb. 4, 1941 2,373,642 Backofen et al. Apr. 17, 1945 2,391,972 I-lulford et a1. Jan. 1, 1946 2,581,600 Pateras Pescara Jan. 8, 1952 2,792,790 Capps May 21, 1957 2,815,641 Ramsey et al Dec. 10, 1957 2,966,776 Taga Jan. 3, 1961 2,978,986 Carder et al Apr. 11, 1961 3,024,591 Ehrat et a1 Mar. 13, 1962 

1. IN COMBINATION: A FREE PISTON ENGINE WHICH INCLUDES MEANS FOR DEVELOPING PRESSURE IN A LIQUID AND ALSO INCLUDES A NUMBER OF REBOUNCE CHAMBERS CORRESPONDING TO THE NUMBER OF PISTONS THEREIN, A FLUID MOTOR, MEANS INCLUDING HYDRAULIC MEANS FOR COUPLING SAID PRESSURE-DEVELOPING MEANS TO THE INPUT OF SAID MOTOR SAID REBOUNCE CHAMBERS BEING CONSTRUCTED TO BE FREE FROM ANY LIQUID AND TO SUPPLY THE PREDOMINANT RESTORATIVE REBOUNCE FORCE FOR THE PISTON OF SAID ENGINE, WHEREUPON SAID FLUID MOTOR IS DRIVEN IN RESPONSE TO THE OPERATION OF SAID ENGINE, AND 